Upconversion FRET quantitation: the role of donor photoexcitation mode and compositional architecture on the decay and intensity based responses

Lanthanide-doped colloidal nanoparticles capable of photon upconversion (UC) offer long luminescence lifetimes, narrowband absorption and emission spectra, and efficient anti-Stokes emission. These features are highly advantageous for Forster Resonance Energy Transfer (FRET) based detection. Upconverting nanoparticles (UCNPs) as donors may solve the existing problems of molecular FRET systems, such as photobleaching and limitations in quantitative analysis, but these new labels also bring new challenges. Here we have studied the impact of the core-shell compositional architecture of upconverting nanoparticle donors and the mode of photoexcitation on the performance of UC-FRET from UCNPs to Rose Bengal (RB) molecular acceptor. We have quantitatively compared luminescence rise and decay kinetics of Er3+ emission using core-only NaYF4: 20% Yb, 2% Er and core-shell NaYF4: 20% Yb @ NaYF4: 20% Yb, 5% Er donor UCNPs under three photoexcitation schemes: (1) direct short-pulse photoexcitation of Er3+ at 520 nm; indirect photoexcitation of Er3+ through Yb3+ sensitizer with (2) 980 nm short (5-7 ns) or (3) 980 nm long (4 ms) laser pulses. The donor luminescence kinetics and steady-state emission spectra differed between the UCNP architectures and excitation schemes. Aiming for highly sensitive kinetic upconversion FRET-based biomolecular assays, the experimental results underline the complexity of the excitation and energy-migration mechanisms affecting the Er3+ donor responses and suggest ways to optimize the photoexcitation scheme and the architecture of the UCNPs used as luminescent donors

Giant nonlinear optical responses from photon avalanching nanoparticles

Avalanche phenomena leverage steeply nonlinear dynamics to generate disproportionately high responses from small perturbations and are found in a multitude of events and materials, enabling technologies including optical phase-conjugate imaging, infrared quantum counting, and efficient upconverted lasing. However, the photon avalanching (PA) mechanism underlying these optical innovations has been observed only in bulk materials and aggregates, and typically at cryogenic temperatures, limiting its utility and impact. Here, we report the realization of PA at room temperature in single nanostructures--small, Tm-doped upconverting nanocrystals--and demonstrate their use in superresolution imaging at near-infrared (NIR) wavelengths within spectral windows of maximal biological transparency. Avalanching nanoparticles (ANPs) can be pumped by continuous-wave or pulsed lasers and exhibit all of the defining features of PA. These hallmarks include excitation power thresholds, long rise time at threshold, and a dominant excited-state absorption that is >13,000x larger than ground-state absorption. Beyond the avalanching threshold, ANP emission scales nonlinearly with the 26th power of pump intensity. This enables the realization of photon-avalanche single-beam superresolution imaging (PASSI), achieving sub-70 nm spatial resolution using only simple scanning confocal microscopy and before any computational analysis. Pairing their steep nonlinearity with existing superresolution techniques and computational methods, ANPs allow for imaging with higher resolution and at ca. 100-fold lower excitation intensities than is possible with other probes. The low PA threshold and exceptional photostability of ANPs also suggest their utility in a diverse array of applications including sub-wavelength bioimaging, IR detection, temperature and pressure transduction, neuromorphic computing, and quantum optics.Comment: 14 pages, 4 figure

GSK3β activity alleviates epileptogenesis and limits GluA1 phosphorylationResearch in context

Background: Glycogen synthase kinase-3β (GSK3β) is a key regulator of cellular homeostasis. In neurons, GSK3β contributes to the control of neuronal transmission and plasticity, but its role in epilepsy remains to be defined. Methods: Biochemical and electrophysiological methods were used to assess the role of GSK3β in regulating neuronal transmission and epileptogenesis. GSK3β activity was increased genetically in GSK3β[S9A] mice. Its effects on neuronal transmission and epileptogenesis induced by kainic acid were assessed by field potential recordings in mice brain slices and video electroencephalography in vivo. The ion channel expression was measured in brain samples from mice and followed by analysis in samples from patients with temporal lobe epilepsy or focal cortical dysplasia in correlation to GSK3β phosphorylation. Findings: Higher GSK3β activity decreased the progression of kainic acid induced epileptogenesis. At the biochemical level, higher GSK3β activity increased the expression of hyperpolarization-activated cyclic nucleotide-gated (HCN) channel 4 under basal conditions and in the epileptic mouse brain and decreased phosphorylation of the glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunit GluA1 at Serine 831 under basal conditions. Moreover, we found a significant correlation between higher inhibitory GSK3β phosphorylation at Serine 9 and higher activating GluA1 phosphorylation at Serine 845 in brain samples from epileptic patients. Interpretation: Our data imply GSK3β activity in the protection of neuronal networks from hyper-activation in response to epileptogenic stimuli and indicate that the anti-epileptogenic function of GSK3β involves modulation of HCN4 level and the synaptic AMPA receptors pool. Keywords: Glycogen synthase kinases-3, GSK3, Epilepsy, AMPA receptors, GluA1 phosphorylatio

The clinical and epidemiological profile of paediatric-onset multiple sclerosis in Poland

Background. Paediatric-onset MS (POMS) has a unique clinical profile compared to the more prevalent adult-onset MS. For this study, we aimed to determine the demographic and clinical characteristics of POMS in Poland as well as addressing some of its epidemiological aspects. Methods. A retrospective study was conducted based on the Polish Multiple Sclerosis Registry, considering a population of children and adolescents with MS (age ≤ 18 years). Data were collected by all 13 centres across Poland specializing in diagnosing and treating POMS. The actual course of the disease and its clinical properties were compared between child (≤12 years) and juvenile (>12 years) patients. MS onset and its prevalence were assessed at the end of 2019, stratified by age range. Results. A total of 329 paediatric or juvenile patients (228 girls, 101 boys) with a clinically definite diagnosis of MS, in conformity with the 2017 McDonald Criteria, were enrolled. For 71 children (21.6%), the first symptoms appeared before the age of 12. The female: male ratio increased with age, amounting to 1:1 in the ≤12 years group and to 2.9:1 in the >12 years group. In most cases, the disease had multi-symptomatic onset (31.3%), and its course was mostly of a relapsing–remitting character (95.7%). The initial Expanded Disability Status Score for both groups was 1.63 ± 1.1, whereas the annual relapse rate was 0.84 during the first 2 years. The time between the onset of symptoms and diagnosis was longer in the younger patients (8.2 ± 4.2 vs. 4.6 ± 3.6 months; p < 0.005). On 31 December 2019, the age-adjusted prevalence standardized to the European standard population was 5.19/100,000 (95% CI, 4.64–5.78). Significantly higher prevalence was noted in the 13–18 years group (7.12; 95% CI, 6.64–7.86) than in the 9–12 years group (3.41; 95% CI, 2.98–3.86) and the <9 years group (0.56; 95% CI, 0.46–0.64; p < 0.001). Conclusion. POMS commencing at the age of ≤12 years is rare, differing significantly from the juvenile-onset and adult MS in terms of clinical characteristics, course, and incidence, as stratified by gender

Mapping chromatin accessibility and active regulatory elements reveals pathological mechanisms in human gliomas

Chromatin structure and accessibility, and combinatorial binding of transcription factors to regulatory elements in genomic DNA control transcription. Genetic variations in genes encoding histones, epigenetics-related enzymes or modifiers affect chromatin structure/dynamics and result in alterations in gene expression contributing to cancer development or progression. Gliomas are brain tumors frequently associated with epigenetics-related gene deregulation. We perform whole-genome mapping of chromatin accessibility, histone modifications, DNA methylation patterns and transcriptome analysis simultaneously in multiple tumor samples to unravel epigenetic dysfunctions driving gliomagenesis. Based on the results of the integrative analysis of the acquired profiles, we create an atlas of active enhancers and promoters in benign and malignant gliomas. We explore these elements and intersect with Hi-C data to uncover molecular mechanisms instructing gene expression in gliomas. Gliomas are tumors often associated with epigenetics-related gene deregulation. Here the authors reveal an atlas of active enhancers and promoters in benign and malignant gliomas by performing whole-genome mapping of chromatin accessibility, histone modifications, DNA methylation patterns and transcriptome analysis simultaneously in multiple tumor samples